All the Unity licenses are a one time payment. No yearly.
Well I guess I should have mentioned we want to get into enterprise mobile development not game development.
You shouldn't really use any of these game engines for anything other then creating games.
Frameworks suitable for the enterprise apps aren't really suitable for games and vice versa. You *can* do it, but really you want to use the right tools for the job.
Agreed...use the right tool for the job. Just like GameMaker is better for 2d games, and Unity3d is better for 3d games, neither of these is good for non-game apps. sure, GameMaker has a bit of 3d, and you can use Unity3d to make 2d games, both can make non-game apps, but really, it isn't worth the workarounds you need.